The present invention relates to a dial and pointer electrical instrument comprising a movement, carrying a pointer, and a scale in a cylindrical housing closed at one end by a glass through which the pointer is read against the scale and closed at the other end by a base carrying terminal structure which electrical connection from outside the housing to the movement inside the housing is effected, the movement being attached to a mounting structure which positions the movement inside the cylindrical housing and being retained therein by fixing devices cooperating with the housing, without mechanical attachment of the movement to the base. The word "glass" is used for convenience without regard for the material thereof. Such instruments are used, for example, as indicators in aircraft. The invention is concerned with the problem of being able to meet a range of requirements with economical stocking of standard parts, also with improved hub lighting arrangements suitable for small size instruments, and also with an improved means for mounting the glass of the instrument.
"Size" herein refers to cross-sectional dimensions, i.e. diameter for the typical case of a circular cylindrical housing. In a range of instruments it will typically be necessary to provide several different sizes; for each size different depths of housing may be required, different types of movement may be required and it may be necessary to incorporate a signal conditioning circuit, e.g. a circuit which scales the input electrical signal to the input signal to the movement. It is also commonly necessary to make the housing airtight so that it can be sealed with a fill of an inert gas, especially for use in aircraft.